1. Field of the Invention
The present invention relates generally to gas turbine engines and, more particularly, to a precooling heat exchange arrangement integral with a mounting structure fairing of a gas turbine engine for precooling high pressure hot bleed air.
2. Description of the Prior Art
Many commercial aircraft gas turbine engines employ high pressure hot air bled from the core engine compressor for use by different systems on the aircraft. In particular, the high pressure air is required by a variety of tasks on the aircraft, one such task being passenger cabin cooling. Prior to use of the air, the temperature of the air must be lowered to reasonable levels in accordance with the requirements of the specific task. For instance, air supplied for cooling the passenger cabin before the aircraft has ascended above approximately twenty thousand feet has to be first precooled by a heat exchanger and then finally cooled by an air conditioning system on the aircraft.
One current method of precooling the high pressure compressor bleed air is to extract or bleed air from the engine fan duct aft of the outlet guide vanes of the engine nacelle. The cooler bleed air from the fan duct and the high pressure hotter bleed air from the core engine compressor are then passed through a heat exchanger where the hotter high pressure air gives up some of its thermal energy to the cooler fan duct bleed air.
Use of the precooling heat exchange process is necessary, although, current systems for attaining heat transfer are unduly complex. In one system, an elaborate layout of piping is employed to pass the high pressure bleed air to the aircraft and to route the cooler fan duct bleed air to the location of the heat exchanger. By the time the cooler fan duct bleed air reaches the heat exchanger and performs its cooling task, it has lost most of its thrust potential due to frictional losses because of various bends and turns of the piping. As a result, the fan duct bleed air is discharged overboard at a loss to the propulsion system thermodynamic cycle.
Consequently, a need still remains for improvements in the arrangement for performing precooling heat transfer operations which will more fully utilize the cooler fan duct bleed air.